1. Field of the Invention
This invention relates to a resin composition for encapsulating a semiconductor chip and a semiconductor device therewith.
2. Description of the Related Art
Recently, epoxy resin compositions have been predominantly used for encapsulating a semiconductor chip because of their good balance among productivity, a cost and reliability. Along with reduction in a size and a thickness in a semiconductor device, an epoxy resin composition for encapsulating with a lower viscosity and higher strength has been needed. Furthermore, in terms of environmental concerns, it has been increasingly needed to make a device having flame retardance without a flame retardant such as Br compounds and antimony oxide. From such a situation, there has been recently a distinctive tendency to employing a less viscous resin and adding more inorganic fillers to an epoxy resin composition. As a new trend, a semiconductor device has been more frequently mounted using an unleaded solder with a higher melting point than a conventional solder. For applying such a solder, a mounting temperature must be higher by about 20° C. than a conventional temperature, and thus a mounted semiconductor device becomes considerably less reliable than a device of the related art. Therefore, the need for improving reliability in a semiconductor device by providing a higher-level epoxy resin composition has increasingly become stronger, which further accelerates reducing a resin viscosity and increasing the amounts of inorganic fillers.
As well-known technique, a low viscosity and a high flowability during molding can be maintained by using a resin with a lower melt viscosity (see, Japanese Laid-open Patent Publication NO. 1995-130919) or by surface-processing inorganic fillers with a silane coupling agent for increasing the amounts of the inorganic fillers (see, Japanese Laid-open Patent Publication NO. 1996-20673). However, any of these methods cannot simultaneously meet all requirements of crack resistance during soldering, higher flowability and flame retardance.
Therefore, an epoxy resin composition comprising phenol aralkyl epoxy resin containing biphenylene structure and phenol aralkyl hardener containing biphenylene structure, which are excellent in crack resistance during soldering and flame retardance, is proposed in the name of Sumitomo Bakelite Co. Ltd., who is the present assignee (see, Japanese Laid-open Patent Publication No. 1999-140277). Since such an epoxy resin composition contains many aromatic rings in a molecular structure, the epoxy resin composition is burnt to form a carbonized layer at the surface of moldings therewith, so that further burnings may be restrained and that the epoxy resin composition may show the excellent flame retardance. Further, the improvement of the crack resistance during soldering is contributed by the improvement of hydrophobicity by containing an aromatic ring structure, and the lowering elastic modulus at high-temperature by growing in the distance between cross-linking points.